Dual-homed no routing

[tgif]

I have setup a dual-homed redhat machine as a firewall, I am able to ping the two network cards from both the router and the inside network. I however can't ping the router from the inside network and I can't ping the inside network from the router.
I have disabled ipchains still with no luck. I aslo enabled and disable ip forwarding with no luck.

Any help would be appreciated.

 

[d3vNull]

can you type
netstat -nr
and see if all the routes are listed as expected/required?